1. Field of the Invention
The present invention generally relates to a single-side embossed color steel sheet having printability, and, more particular, to a single-side embossed color steel sheet, which is produced via a process of printing on an embossed side of the steel sheet to exhibit various feelings of texture and colors so that an irregular surface of the steel sheet exhibits a remarkable feeling of solidity, and has enhanced contaminant resistance properties and environmental friendliness, thereby satisfying demands of functionality and aesthetic design at the same time.
2. Description of the Related Art
Recently, in a market of household appliances, consumers regard an aesthetic design as one of the most important choice criteria as well as basic functionality when choosing the household appliances, and thus manufacturers also try to satisfy such demands of the consumers via diversification of aesthetic design, a feeling of texture or a feeling of color of products, and via development of high quality products. In addition to the fundamental function and the diversification of the aesthetic design, the manufactures are also confronted with a difficulty in that it is necessary to produce environmentally friendly products using harmless materials in preparation for tough environmental regulations which will likely be adopted in many countries around the world.
Conventional color steel sheets with an embossed surface include a single-side embossed steel sheet, and a double-side embossed steel sheet which has a similar appearance to the single-side embossed steel sheet. The single-side embossed steel sheet is manufactured by the steps of compressing one side of a steel sheet with a metal roller (emboss roller) having a predetermined pattern formed thereon upon skin-pass rolling of cold rolling to form an embossed pattern on the one side of the steel sheet, performing electro plating or hot-dip plating on the embossed side to form a galvanized coating or other well-known coatings, performing a general pre-treatment including a chromic acid treatment, and spray printing in a sheet manner. The double-side embossed steel sheet is produced by the steps of printing a steel sheet using paints for pre-coated metal (PCM), and compressing the painted steel sheet with a double-side embossing rollers.
One of the conventional techniques is disclosed in Korean Patent No. 197932, entitled “Color steel sheet with one side embossed, and method thereof.” This patent addresses problems related to defective coat adherence caused on the surface of both sides of crease of an irregular portion, pores/bubbles around an embossed portion of a single-side embossed steel sheet which will be subjected to a PCM painting treatment, and defects caused by the irregularity on the steel sheet. In this regard, this patent solves these problems by developing a new plating technique and paints, and specifically, improves treatment conditions and a method thereof. However, this patent has a disadvantage in that, since a resin (in particular, a top coat) of the disclosure causes a color difference (non-uniform covering power) at an angled portion with surface irregularity formed thereon, and is poor in deep drawability, thereby failing to obtain steel sheets having optimal properties. Furthermore, it also has a disadvantage in that since the surface appearance also depends only on an embossed irregular pattern, the steel sheet has a simple appearance.
Another conventional technique is disclosed in Korean Patent No. 442192, entitled “Color steel sheet with one side embossed.” The single side embossed color steel sheet of the disclosure is formed by the steps of forming a well-known chromate layer on one embossed side of a steel sheet, forming a polyester primary coat of a high workability on the chromate layer, and forming a top coat using a polyester resin as a primary resin in addition of other resins. This patent solves a problem of environmental contamination caused by a conventional plating process while providing a natural appearance to the steel sheet by forming irregularity or corrugation on the surface of the steel sheet. However, since such irregularity or corrugation on the surface of the steel sheet can be expressed only in a single color, the steel sheet provides a monotonous feeling of color, thereby failing to satisfy demands of the consumers. Furthermore, since the steel sheet is manufactured by use of some detrimental materials whose use must be suppressed in terms of environmental regulations, the steel sheet of the disclosure does not satisfy requirements for environmental friendliness from around the world.
In terms of a plating method for producing a PCM color steel sheet, although two-roll natural type or two-roll reverse type roll coating method has been applied to a construction material which does not have a significant emphasis on an appearance, this method is difficult to precisely adjust a paint thickness, and is likely to suffer from popping and roll marks.
Accordingly, although a three-roll reverse type coating method overcoming such a problem as mentioned above has been typically applied to a color steel sheet for household appliances which have an emphasis on their appearance, this method also has problems in that it is difficult to freely control a paint thickness due to irregularity of the surface which is a property of an embossed substrate, and in that a manufacturing speed is lowered.